"""Permanent deletion shared by the trash API and scheduled retention cleanup."""
from django.db import transaction
from .models import DriveItem, UploadSession
from .services import descendant_files
from .storage_layout import disk_path, file_location


def has_active_uploads_in_tree(item):
    """Do not purge directories while a resumable upload targets a descendant."""
    if not item.is_folder:
        return False
    pending = [item.pk]
    while pending:
        batch, pending = pending[:250], pending[250:]
        if UploadSession.objects.filter(parent_id__in=batch).exists():
            return True
        pending.extend(DriveItem.objects.filter(parent_id__in=batch, is_folder=True).values_list('pk', flat=True))
    return False


def delete_trashed_item(item):
    """Delete the SQL tree, then its tracked files after commit.

    Untracked files and directories are not erased. Failures resolving a stored
    path abort before the SQL delete; missing physical files are tolerated.
    """
    if item.trashed_at is None:
        raise ValueError('L’élément doit être dans la corbeille.')
    if has_active_uploads_in_tree(item):
        raise ValueError('Un transfert est encore en cours dans ce dossier.')
    files = [disk_path(key) for key in descendant_files(item)]
    # A child may have been trashed separately, into another isolated directory.
    folders = []
    queue = [item.pk] if item.is_folder else []
    if item.is_folder:
        folders.append(disk_path(item.storage_location or file_location(item.space, item.parent, item.name)))
    while queue:
        batch, queue = queue[:300], queue[300:]
        children = list(DriveItem.objects.filter(parent_id__in=batch, is_folder=True).select_related('parent','space'))
        queue.extend(child.pk for child in children)
        for child in children:
            folders.append(disk_path(child.storage_location or file_location(child.space, child.parent, child.name)))
    with transaction.atomic():
        item.delete()
        def remove_files():
            for path in files:
                path.unlink(missing_ok=True)
            for folder in sorted(set(folders), key=lambda p:len(p.parts), reverse=True):
                if folder.is_dir() and not folder.is_symlink():
                    # Never recursively erase untracked files.
                    try: folder.rmdir()
                    except OSError: pass
            # Remove empty UUID trash containers (never the shared .trash root).
            trash_root = disk_path('.gooddrive-trash')
            for path in [*files, *folders]:
                parent = path.parent
                while parent != trash_root and parent.is_relative_to(trash_root):
                    try: parent.rmdir()
                    except OSError: break
                    parent = parent.parent
        transaction.on_commit(remove_files)